Check if any year is a leap year, find all leap years in a date range, and calculate how many Feb 29th birthdays you've actually celebrated. Includes the complete 400/100/4 rule explanation.
🔍 Is This Year a Leap Year?
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Rule-by-Rule Breakdown
📐 The 3-Rule Gregorian Leap Year Formula
isLeap(year) =
(year % 4 === 0)
AND (year % 100 !== 0)
OR (year % 400 === 0)
÷4
Rule 1
Divisible by 4 → leap year candidate
÷100
Rule 2
Divisible by 100 → NOT leap (exception)
÷400
Rule 3
Divisible by 400 → IS leap (override)
Why these rules? A solar year is ~365.2422 days. Adding 1 day every 4 years (÷4 rule) gives 365.25 — slightly too many. Removing century years (÷100) corrects to 365.24. Adding back every 400th year (÷400) gives 365.2425 — close enough that the error accumulates only 1 day over ~3,300 years.
📆 Upcoming Leap Years (2024 – 2100)
Every 4 years — except 2100 which is divisible by 100 but not 400, so it is skipped.
Current yearLeap year
📜 Notable Leap Year History
Year
Type
Notable Event / Rule
📊 Find All Leap Years in a Range
🎂 Feb 29 Leap Year Birthday Calculator
Born on February 29? Find out how many real Feb 29 birthdays you've had, how old you are in "leap years", and your next Feb 29 birthday.
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🌍 Feb 29 Birthdays — Fun Facts
🎲 Probability: 1 in 1,461 people are born on Feb 29 (0.068% of all birthdays).
🌍 Leaplings worldwide: Approximately 5 million people globally are born on Feb 29.
📜 Legal age: In most countries, leaplings legally turn (e.g.) 18 on March 1 in non-leap years. In Hong Kong, Feb 28 is used.
🏛️ Famous leaplings: rapper Ja Rule (1976), motivational speaker Tony Robbins (1960), and Pope Paul III (1468).
💍 Leap Day tradition: In Ireland and Scotland, Feb 29 is "Bachelor's Day" — women are allowed to propose to men. If refused, the man owes a gift (traditionally gloves or a silk gown).
❓ Frequently Asked Questions
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AI Calendar Assistant — Coming Soon!
Ask AI about leap year effects on your birthday, date calculations, and calendar history.